Intravascular catheters are widely used for a variety of diagnostic and therapeutic purposes. Catheters are used to place various treatment materials, such as drugs and devices, within remote regions of the body. Specifically, in the treatment of the circulatory system via percutaneous transluminal angioplasty (PCTA) catheters are utilized having balloons on their distal ends. These catheters treat narrowed regions or stenoses in the vascular system by expanding the balloon in a region of the vessel having plaque build-up and pressing the plaque radially outward into the vessel wall. Angioplasty has been developed as an alternative to bypass surgery for treating vascular diseases or other conditions that cause occlusion or reduction of blood flow in a patient's vascular system.
To access and treat such vascular maladies, catheters are moved through the circulatory system to a selected site with the assistance of a guide wire. The guide wire may be fixedly attached to the catheter. Also, the guide wire may be slidably accommodated within the catheter. The guide wire may pass through the main lumen of the catheter or through a separate lumen that extends parallel to the main lumen of a multi-lumen catheter.
Multi-lumen catheters commonly include a main lumen and at least one secondary lumen. The main lumen is typically used for balloon inflation or deflation, irrigation, delivery of drugs or other treatments and to facilitate the insertion of other surgical devices, such as an angioscope. The secondary lumen is typically used for accommodating the guide wire.
Catheters having a separate, secondary, guide wire lumen extending throughout the length of the catheter are often referred to as “over-the-wire” catheters. Catheters having a guide wire lumen that only extends through the distal portion of the catheter are referred to as “single-operator-exchange” or “rapid exchange” catheters. The single operator exchange or rapid exchange catheters have a shortened guide wire lumen which extends from the distal end of the catheter to a location just proximal to a “payload” area, or the location of the treatment drug or device, such as a dilation balloon or a stent. Rapid exchange catheters advantageously reduce the amount of friction generated as the guide wire slides through the catheter and enhances the feel and responsiveness of the catheter to a physician.
Because it may be necessary for a catheter to access a remote site within the vascular system, catheters must pass through increasingly narrow and tortuous pathways with sharp bends and curves. To effectively traverse these remote pathways of the vasculature, catheters must be designed with certain key characteristics. First, the catheter assembly must have sufficient stiffness or “pushability” to enable a longitudinal force to be transmitted through the assembly so that the physician can advance or push the catheter through the vasculature to the site of a stenosis.
Secondly, the catheter must also be sufficiently flexible so that the catheter tip can pass through the sharp bends of the increasingly narrow blood vessels. This flexibility, often referred to as “trackability,” allows the physician to manipulate the catheter through a patient's vascular system.
While there are a number of different ways in which catheters may be designed to have the desired pushability and trackability characteristics, many catheters are currently constructed with a reinforcing element. This reinforcing element typically includes a braided material or, sometimes, a spirally wound material. Braided reinforcement elements are particularly useful for providing axial strength to the exterior tube of a multi-lumen catheter because the multi-lumen catheter is particularly susceptible to kinking or ovalization of the circular cross-sections of the various lumens when the catheter is exposed to a high flexure or a high torsion, such as when the catheter is passed through the bends or turns of the vascular system.
As the use of angioplasty, stent delivery, drug delivery and other intravascular procedures continues to increase, there is a continuing need to provide new, reinforced multi-lumen catheters with improved trackability and pushability qualities and which can be easily manipulated for guide wire exchanges.